This study investigates the optimization of solid alcohol synthesis from Supernatant-Waste Cooking Oil (S-WCO) using Response Surface Methodology (RSM) combined with Box-Behnken Design (BBD). The primary objective was to determine the optimal conditions for maximizing the yield of solid alcohol by systematically varying three key parameters: mass of oil (5, 10, 15 g), NaOH to oil ratio (0.100, 0.175, 0.250 g/g), and heating time (20, 30, 40 minutes). The experimental findings revealed that the yield of solid alcohol ranged from 81.20% to 87.67%, with the highest yield achieved at mass of oil of 11.14 g, NaOH to oil ratio of 0.20 g/g, and heating time of 25.70 minutes. The desirability value for these conditions was calculated to be 0.911, indicating the process's high efficiency. Analysis of variance (ANOVA) substantiated the model's significance, highlighting the critical influence of both linear and quadratic terms, particularly the NaOH to oil ratio and heating time.The results have profound implications for scaling up the process in industrial contexts, offering a promising solution for waste management and alternative energy production. Future research should explore the potential of alternative catalysts and further process optimizations to enhance the economic and environmental benefits of this method.